The present invention relates to containers and their closures and is particularly applicable to consumer-sized containers and their closures for carbonated beverages or other contents under pressure.
The maximum size of the mouth, or opening, of a container with contents under pressure is principally determined by the level of pressure inside the container and the characteristics of the mechanism(s)—such as twist threads—that are used to secure the closure, or “cap,” to the container. The force on the cap induced by the pressurized contents may be calculated by the pressure inside the container (measured, for example in pounds-per-square-inch, or “psi”) multiplied by the area of the inside of the cap that is exposed to the interior of the container. For a given level of pressure, this “internal force” is thus proportional to the square of the radius of the opening of the container.
As a result of the foregoing, the opening of commercially produced screw-top beer and soda (or “pop”) bottles is constrained to be that for which twist threads of a commercially acceptable size and strength will provide enough counteracting “holding force” to hold the cap securely. Twist threads for soda or beer bottles that are commercially practical and acceptable to consumers have a maximum depth (i.e. dimension perpendicular to the container side wall) of approximately 2.5 mm. Such threads provide a certain maximum holding force. Exceeding this maximum would give rise to the possibility that a significant portion of the contents could escape and/or the cap could be dislodged from its position on the container, for any of a number of reasons. For example, the twist threads might slip and become disengaged if, for example, the cap distorted due to increased pressure—and thus increased force on the cap—resulting from the container being left in a warm car or shipping truck. Or there might be at least enough force on the inside of the cap that the sealing between the inside of the cap and the container rim could be breached and a significant portion of the contents could leak from the container. (We use the word “significant” here to distinguish from the minute amounts of gas that inevitably may leak from a container over very long periods of time (years or perhaps decades.) In a worst-case scenario, the cap could be dislodged, ejected from the container altogether, and sent flying.
In light of the above considerations, the opening of a screw top (typically all-aluminum) beer bottle is limited to an inner diameter of no more than about 30.5 mm. The corresponding cap has an outside diameter of about 38 mm. The pressure inside a typical beer bottle is about 30 psi. This is about 40% less than the psi inside a typical soda bottle, which is approximately 50 psi. As a result the opening of a soda bottle must be smaller than for beer, given the same twist thread capability, so that the internal force can be kept to an acceptable level. Indeed, screw top plastic soda bottles are typically limited to an opening of no more than about 22.5 mm in inner diameter, with a corresponding outside cap diameter of about 28 mm.
These constraints are commercially vexing in that it would desirable if containers for beer, soda and the like could have wider openings. For example, there is a loss of flavor/taste when one drinking a commercially-filled beverage from a relatively small opening. Such loss of flavor/taste could be reduced or eliminated if the container were have a wider opening—at least in part because it allows oxygen into the beverage as the consumer drinks.
One way to deal with this higher level of internal force could be to “beef up” the twist threads. Such twist threads would, however, have to be unacceptably large and/or unsightly for use in a consumer product. Or one might envision cap-securing mechanisms other than twist threads for containers with contents under pressure. Even if such alternatives were devised, the cap-securing mechanism might well have to be in such tight engagement with the container as to make removal extremely difficult for the consumer. Additionally, one would have to be concerned that the container and/or cap might be broken upon the application of a large force in the process of attempting to remove such a tightly secured cap. The result would be the need to “beef-up” the container—using thicker glass or metal, for example—which, disadvantageously, could add to the cost and weight of the container.
Another possibility one might envision is the use of some kind of separate securing mechanism analogous to the wire “cage” securing the cork of a Champagne bottle. Any such separate mechanism would be clumsy and/or inconvenient to remove.
The foregoing are some reasons we believe that industry has not commercialized wider-mouthed containers for carbonated beverages or other contents under pressure.
Consider, also, containers and closures for Champagne or highly carbonated sparkling wines. Here, a common closure is a cork or plastic stopper (usually referred to in either case as a “cork”) secured by a wire cage. Removing the wire cage might be somewhat of an annoyance for some. But the major issue here is that of being able to remove the cork without it flying off and/or without having some of the contents come shooting out. This task requires practice, deftness and, usually not a small degree of hand strength and, as such, is an unacceptably daunting task for many consumers.
Another concern in this realm is that the pressurized gas in a container for a beverage or other contents under pressure should not be allowed to forcibly project a twist-off cap (or other removable closure) away from the container at the moment that the cap begins to be removed (e.g. begun to be twisted off)—thereby turning the cap into a potentially dangerous projectile. To this end, it is known in the context of existing containers to implement one or more venting mechanisms to prevent this from happening. One such mechanism provided in plastic containers, for example, is to provide cuts through the twist threads on the bottle neck, thereby providing a path for escaping gases as the cap begins to be twisted off and the seal between the container rim and the cap is broken. Another mechanism, which is used for aluminum beer bottles, for example, is to provide small holes through the outside wall of the cap near its top, with such holes becoming a path for escaping gases once the cap begins to be twisted off. Yet another mechanism, sometimes applied to plastic ribbed corks used for sparkling wine, for example, is to provide vent holes between at least some of the ribs of the ribbing. As the cork begins to be pulled out of the bottle, those holes become exposed, providing a pathway for gas from the interior of the bottle, into the hollow plastic cork and out the vent holes.
These approaches are adequate to eliminate or substantially reduce the problem of the cap being forcibly projected away from the container during the opening process. However, they may, disadvantageously, disperse gases and, potentially, a certain amount of liquid spray, onto the hands of the consumer.